Yesterday, something significant happened in Rwanda; the year changed from 2018 to 2019. But by the time it happened in Rwanda it had already occurred in other countries such as Uganda and Kenya which are in a different time zone. And in some countries, they were still waiting for their turn to enter the New Year. What is true for each country is that they had to wait 24 hours for this change to occur.

This is to say that it is universally agreed that a day comprises twenty-four hours. But whose decision was it to divide a day into two equal 12-hour periods? Ancient Egyptians started it by dividing day time into 12 hours. They made use of shadow clocks known as sundials. According to ABC Science, a knowledge platform, the way sundials worked was that stakes were placed in the ground and then time was measured by looking at the length and direction of the shadows of the sun.

The ancient Egyptians then divided night time into 12 hours by observing the stars.  By looking at a system of 36 star groups known as ‘decans’, they discovered that every night, one decan would rise 40 minutes after the previous one. Eleven decans in total were observed to rise each night, thereby creating 12 divisions of the night. This is according to Wikipedia, an encyclopedia.

However, according to Curious, a science knowledge website, the Egyptian method of calculating time was faced with a major challenge; daylight lasted longer during summer while night time lasted longer in the winter. Therefore, the number of hours in a day changed from one season to the next.

Because of this, there were irregularities. These were later dealt with by using the sun’s movement along the celestial equator to measure time. This is according to Seeker, an information resource.

In the 14th Century, mechanical clocks were invented in Europe, making it possible to have a consistent measure of a day and finally stamping the 24-hour day as we know it today. This is according to History World, a knowledge dissemination platform.

According to Today I Found Out, an information site, all the methods that have been used up to date have been based on estimates. The mechanical clock, for instance, does not put into account the fact that daytime hours are different from nighttime hours. Nobody knows for sure what time is or how it should be measured. Scientists are still working to improve the accuracy with which time is measured.

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